Why Northern Pike Are Bad for the Kenai Peninsula by Rob Massengill

Refuge Notebook • Vol. 19, No. 46 • November 17, 2017

Why northern pike are bad for the Kenai Peninsula by Rob Massengill

An invasive northern pike removed from Stormy Lake (Nikiski) in 2011. Pike have since been eradicated there and in many other areas on the Kenai Peninsula to protect native fisheries.

The history of northern pike in Southcentral they dart out to catch prey. Pike are less efficient Alaska is murky, but it goes something like this. Pike ambush predators outside this habitat. Some native are not native to Alaska south and west of the Alaska fish like juvenile coho salmon and trout often utilize Range and were likely first introduced to Bulchitna this same habitat making them very susceptible to Lake in the Susitna Drainage in the 1950s. Pike are pike predation. In contrast, deep or fast flowing wa- now in more than 100 waterbodies in this Indiana- ter serves as a refuge for prey as fewer pike inhabit sized drainage. Pike were first documented on the that niche. Looking at fish survey data from Interior Kenai Peninsula near Soldotna Creek in the 1970s and Alaska where native pike are widespread, it is striking have since spread to 23 waterbodies. Pike have trav- how few juvenile salmonids actually coexist with pike eled down the west side of Cook Inlet where commer- in the countless shallow and weedy floodplain lakes cial setnetters occasionally catch them. Fortunately, common to that region despite connectivity to anadro- the same hasn’t been true for Kenai Peninsula setnet- mous rivers. ters. Southcentral Alaska has a lot of shallow vegetated So what’s the big deal with having pike on the waterbodies that for millennia were nurseries for ju- Kenai Peninsula? Here, pike are considered an in- venile salmonids as these fish evolved in the absence vasive species, which can be defined as a non-native of pike. Think of the canoe routes in the Swanson species that causes or is likely to cause economic or and Moose River drainages or lakes in the Soldotna environmental harm. But pike in their native range Creek and Beaver Creek systems—these provide spec- in Alaska appear to coexist just fine with salmon and tacular habitats for native trout and rearing salmon but trout in places like Bristol Bay and many big Interior also for pike. In contrast, the Kenai Peninsula’s glacial drainages. Intuitively, this doesn’t make sense. Bear rivers and deep sockeye rearing lakes would likely not with me as I explain why invasive pike are a big deal support large pike populations because suitable pike to our local native fish. habitat is sparse. Similarly, the world’s largest sockeye Pike are ambush predators—they prefer relatively fishery in Bristol Bay coexists with native pike because shallow, weedy and slow water habitat from which pike habitat is very limited in their rearing areas.

USFWS Kenai National Wildlife Refuge 93 Refuge Notebook • Vol. 19, No. 46 • November 17, 2017

Firsthand I’ve seen how fisheries can collapse Conceivably eagles could drop a live pike into a water- when invasive pike and native fish occupy the same body too. Any of these unintentional mechanisms are habitat. Northern pike completely eliminated rainbow possible but must be rare. trout, Dolly Varden, juvenile coho salmon and even This summer, we confirmed pike in four new lakes threespine sticklebacks from multiple lakes in the Sol- on the Kenai Peninsula, some of these certainly the dotna Creek drainage where water depths rarely ex- result of deliberate introductions. In fact, identities ceed 25 feet. Northern pike nearly extirpated arctic of individuals suspected of introducing pike were re- char and rainbow trout in Stormy Lake (Nikiski) de- ported. It is a Class A misdemeanor to transport or spite lake depths up to 50 feet. Elsewhere, invasive release live fish in Alaska without a permit. Addition- pike have been implicated in the collapse of valuable ally, civil penalties would seek to recoup the costs to salmon runs like the prized king salmon of Alexander remove introduced pike potentially costing the culprit Creek that once supported a multi-million dollar fish- hundreds of thousands of dollars. ing lodge industry, and the sockeye of Shell Lake in So what typically happens after invasive pike are the Skwentna River drainage. removed? Generally, the waters are restocked by For the last decade, my job has focused on pro- ADF&G with the wild native fish assemblage histori- tecting our native fisheries from pike on the Kenai cally found there. In some cases that might be just Peninsula. In most instances, eradicating pike from sticklebacks, in others it could include wild juvenile a waterbody is infeasible with nets alone, so we treat salmon, rainbow trout, Arctic char, Dolly Varden or the water with rotenone, a plant-based pesticide, to sculpins. In lakes previously stocked with hatchery greatly increase the likelihood of success. We have fish, stocking resumes. demonstrated that rotenone can be applied safely and I frequently receive feedback from residents living effectively while staying within the rigorous permit- on lakes where pike were removed and hear things like ting and label requirements. “…we see more birds and frogs near the lake and see Following years of pike removal, there are now fish jumping regularly…”. These are observations that only eight known Kenai Peninsula waterbodies with suggest the ecological balance and biological diversity pike, all close to one another and often referred to of these lakes are being restored. as the Tote Road pike lakes. Fortunately, these lakes which are surrounded mostly by private lands, do not What can you do to help protect our wild fish re- connect to wild salmon or trout waters. So an ar- sources from invasive pike? Probably the most useful gument could be made for leaving these pike alone— thing is to retain and report any pike caught on the some anglers enjoy catching them, so why remove Kenai Peninsula unless it came from the known pike them if they don’t endanger other fish? The simple waters off Tote Road south of Soldotna. Reports can reason is those pike are a source for illegal introduc- be made online at http://www.adfg.alaska.gov/index. tions elsewhere. Soon, the Alaska Department of Fish cfm?adfg=invasive.report or call 1-877-INVASIV. and Game will announce public scoping meetings for Finally, appreciate that pike are not inherently bad the proposed eradication of invasive pike from these fish—pike just do what they are meant to do. Pike lakes next year. This will be an opportunity to learn fishing can be a great year-round experience. How- more about the project and to share your thoughts. ever, the cost of having pike on the Kenai Peninsula is I’ve overheard conversations that suggest pike are that native fish populations suffer and complete loss spreading more by natural mechanisms than by people of some fisheries occur. intentionally releasing them. Pike eggs are sticky and Rob Massengill, a fisheries biologist with the Alaska are broadcast on standing aquatic vegetation around Department of Fish & Game in Soldotna, can be ice-out each spring. The theory is these eggs could reached at 262-9368. Find more information about cling to plane floats or animal legs and then falloff invasive pike at http://www.adfg.alaska.gov/index.cfm? in nearby waterbodies and kick-start new populations. adfg=invasivepike.main.

94 USFWS Kenai National Wildlife Refuge